Comments:
Woad is the common name of the plant Isatis tinctoria and is cometimes listed as Isatis indigotica though this is considered by many to be a newer and invalid name for the same plant. One of its common names is dyer's woad due to the blue dye produced from the plant.

According to Bensky, Clavey and Stoger, in the Chinese Herbal Medicine Materia Medica, the identification of this herb is complex as there are many plants in China called, and used as, the medicinal herb Ban Lan Gen. According to the Chinese Pharmacopoiea, the standard plant is known as Northern Ban Lan Gen, which is Isatis indigotica. Also accepted is a plant known as Southern Ban Lan Gen, which is Baphicacanthus cusia. In the Chinese Herbal Medicine Materia Medica, due to the lack of clarity in precise identification, the herb Ban Lan Gen is referred to as Isatidis/Baphicacanthis Radix.

Growing and Propagation

The 30 species of Isatis are native to central and southern Europe and western and central Asia. In their native habitat, they grow in rocky, dry places and waste ground, hardy in a wide range of climate, in USDA zones 4 to 8. It is a short-lived perennial or biennial that grows 2-4 feet high with flowers that bloom in early summer. The plant grows easily in any soil but prefers moderately fertile, moist, well-drained soil, in full sun. Propagation is by seed sown in spring, or in the fall in containers in a cold frame. Plants can also be divided in the spring.

Harvesting and Preparation

For medicinal use, good quality Ban Lan Gen consists of long, thick, yellow-white roots that have a powdery cross section.